The above-mentioned layers or discontinuous elements are generally placed against one of the rigid substrates (or against the single rigid substrate), between the said substrate and the polymer-based flexible sheet or one of the said sheets. They may also be placed between two flexible or semiflexible substrates which themselves are associated with a rigid substance or may be placed between two rigid substrates. They will be denoted hereafter by the term “active systems.” The glazing may comprise several active systems.
The first types of active system of interest to the invention are in general electrochemical systems, and more particularly electrocontrollable systems of the type in which the glazing has variable energy and/or optical properties. They also include photovoltaic and electroluminescent systems.
These systems have very varied applications: photovoltaic cells convert solar energy into light energy.
Electrocontrollable systems make it possible to obtain, in particular, glazing of which the darkening/degree of vision or filtration of the thermal/solar radiation may be modified at will. These include, for example, viologen-based glazing which allows the light transmission or absorption to be regulated, as described in Patents U.S. Pat. No. 5,239,406 and EP-612 82.
Electroluminescent systems convert electrical energy directly into light, an example being described in Patent FR-2 770 222.
There is also electrochromic glazing which allows the light and thermal transmission to be modulated. This is described, for example, in the Patents EP-253 713 and EP-670 346, the electrolyte being in the form of a polymer or a gel and the other layers being of mineral type. Another type is described in the Patents EP-867 752, EP-831 360, PCT/FR00/00675 and PCT/FR99/01653, the electrolyte this time being in the form of an essentially mineral layer, all of the layers of the system then essentially being mineral: this type of electrochromic system is commonly referred to by the name “all-solid-state” electrochromic system. There are also electrochromic systems in which all of the layers are of the polymer type, and then one speaks of “all-polymer” electrochromic systems.
In general, electrochromic systems comprise two layers of electrochromic material which are separated by an electrolyte layer and flanked by two electrically conducting layers.
There are also systems called “optical valves”: these are polymer-based films in which are dispersed microdroplets containing particles capable of lying in a preferred direction under the effect of an electric field. An example of this is described in the Patent WO 93/09460.
There are also liquid-crystal systems, which operate in a similar way to the previous ones: they use a polymer film placed between two conducting layers and droplets of liquid crystals are dispersed in the said film, especially nematic liquid crystals having positive dielectric anisotropy. When a voltage is applied to the film, the liquid crystals are oriented along a preferred axis, allowing vision. With no voltage applied, the film becomes scattering. Examples of these are described in the Patents EP-238 164, U.S. Pat. No. 4,435,047, U.S. Pat. No. 4,806,922, U.S. Pat. No. 4,732,456. Mention may also be made of cholesteric liquid-crystal polymers, such as those described in the Patent WO 92/19695.
A second type of active system of interest to the invention relates to layers or multilayers whose properties are modified without any electrical supply, due to the effect of heat or light: mention may be made of thermochromic layers, especially those based on vanadium oxide, thermotropic layers and photochromic layers. Within the context of the present invention and throughout the present text, the term “layer” should be taken in its widest sense: the layers may just as well be made of mineral materials as organic-type materials, most particularly polymers, which may be in the form of polymer films or even of gel films. This is especially the case with thermotropic gels, for example those described in the Patents EP 639 450, U.S. Pat. No. 5,615,040, WO 94/20294 and EP 878 296.
A third type of active system of interest to the invention relates to elements in the form of heating wires or grids, or conducting layers heating by the Joule effect (these may be wires embedded in the surface of the thermoplastic sheet, as described for example in the Patents EP-785 700, EP-553 025, EP-506 521 and EP-496 669).
A fourth type of active system of interest to the invention relates to layers or multilayers having solar-control or low-emissivity properties, especially those based on one or more silver layers interspersed by dielectric layers. These multilayers may be deposited on one of the rigid substrates or on a flexible substrate of the PET (polyethylene terephthalate) type which is placed between two sheets of thermoplastic polymer of the PVB (polyvinyl butyral) type joining together the two rigid substrates of the glass type. Examples of these are found in the Patents EP-638 528, EP-718 250, EP-724 955, EP-758 583 and EP-847 965.
Some of these systems require means of electrical connection to an external current source, which must be designed so as to avoid any short circuit. All these systems have in common the fact that they may, to a greater or lesser extent, be sensitive to mechanical or chemical attack, to contact with water or to exchanges with the outside.
These are the reasons why, in order to preserve their correct operation, these active systems are usually placed against at least one protective carrier substrate. They are usually placed between two protective substrates, for example made of glass, or made of a rigid, semirigid or flexible polymer, either by direct contact or via one or more thermoplastic-type joining polymer sheets. They usually have the laminated structure described above. Peripheral sealing means are often provided, the purpose of which is to isolate the active system as far as possible from the outside. It is general practice to use butyl rubber seals combined with silicone or polysulphide seals, which are capable, in particular, of limiting the diffusion of water from the active system to the outside, and vice versa.
However, these seals are capable of improvement on several counts since they must meet as best as possible at least three requirements which are not necessarily compatible. Firstly, as we have seen, they must isolate the active system from the outside. They must therefore act as efficiently as possible as a barrier, especially to water in vapour form. The seals used hitherto are not entirely satisfactory from this standpoint. Secondly, their fitting—the way in which they are placed along the edge of the devices—is not necessarily the simplest from the industrial point of view. Finally, their mechanical properties can be well below what is required.